Hi everyone, i am running a new asdl line. i used to run a cablemodem connection that asign the public ip address directly to the mikrotik wan interface (eth3).

The adsl modem is a cheap one that my isp gives to new clients, so i cant make port forwarding or things like that. I configure the device in BRIDGE mode and whit my windows PC and a direct PPOE connection everything works fine. When i configure the pppoe client in the mikrotik an change the masquerade rule, internet works in all the pcs connected to it, but some url dont respond.

I can not surf the web normally. I tried changing the MTU but nothing seems to fix the problem. Web sites like microsoft.com or the forum.mikrotik.com never respond.

Anyone has a clue?

Thanks a lot.

what about tracing the route to these sites?

1. Make sure you have the ip address assigned by modem, and check the routing tables. You should have default gateway routing and the ip address itself. Be sure to check the DNS Servers assigned also. Check with ping. Got reply ?
2. Give the report of pinging the host: http://www.mikrotik.com , what is the ip ?
3. Open the command prompt windows, type like this below:

C:\> telnet http://www.mikrotik.com 80

Hit ENTER after that, wait .. if your screen turn and goes blank, it means connected.
If not, there is something wrong


- Rio.Martin -

what about tracing the route to these sites?

could you show me how to do this? Thanks

what about tracing the route to these sites?

could you show me how to do this? Thanks

in command prompt, type

Check your MTU too. Should be 1400 or so. Less than 1460.

Did you do this?

http://forum.mikrotik.com/viewtopic.php ... t=&p=76334

MT is not that great for a PPPoE router. I was hoping to use some of them for certain customers but it's just not reliable. Those mangles rules work in my office but if I take the same router to a customer site it doesn't work so I just stopped trying. Hopefully one day MT will make them auto like every other router out there so we don't need mangle rules or anything like that, just plug and play.

Thanks everyone for the answers.

I found the solution in another post of this forum:

[url]http://forum.mikrotik.com/viewtopic.php ... U+Problems[/url]

Only need is to add a mangle rule:

add chain=forward protocol=tcp out-interface=cityconnect tcp-flags=syn action=change-mss new-mss=1440

Now everything works fine.

I don´t know exactly what the rule does, but i read that the mss-tcp option in the pppoe profile did not work, so this rule solves the MTU fragmentation problem.

Another solution was adding this other rules:

/ ip firewall mangle
add chain=forward tcp-flags=syn action=jump jump-target=mss comment="\[tcp\], mss" disabled=no
add chain=mss protocol=tcp tcp-flags=syn tcp-mss=!536-1460 action=change-mss new-mss=1440 comment="\[tcp\], mss fixation" disabled=no
add chain=mss protocol=tcp tcp-flags=syn tcp-mss=1453-65535 action=change-mss new-mss=1440 comment="\[tcp\], mss 1440 for mtu 1492" disabled=no
add chain=mss protocol=tcp tcp-flags=syn action=change-mss new-mss=clamp-to-pmtu comment="\[tcp\], mss clamp-to-pmtu" disabled=no
add chain=prerouting action=change-ttl new-ttl=set:65 comment="\[tcp\], mss ttl fix" disabled=no

I don´t test this ones, the first one works for me.

Thanks a lot for the interest in this topic and for the posts in the forums that help me with this problem.